Summary: Although the Internet is playing an increasingly significant role in global communication, it remains vulnerable to malicious traffic such as worms and DoS/DDoS attacks. In the last few years, the emergence of high speed active worms, such as Code Red II, Nimda, SQL Slammer and MS Blaster, has become a serious issue. These worms cause serious damage to communication networks throughout the world by using up network bandwidth. In addition, since conventional firewall systems are located just in front of the server and do not prevent malicious traffic from entering the network, they cannot prevent such network congestion. Therefore, the firewall between domains or between core routers should play important roles in the photonic networks. We have developed a prototype system of a network firewall using reconfigurable processors. In this paper, we overview the developed system and present its evaluation results.